Applications of Exoelectron Emission to Nondestructive Evaluation of Alloying, Crack Growth, Fatigue, Annealing, and Grinding Processes

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

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A unification of small- and large-crack growth laws

Fatigue & Fracture of Engineering Materials & Structures ◽

10.1046/j.1460-2695.1999.00149.x ◽

1999 ◽

Vol 22 (8) ◽

pp. 711-722

Author(s):

Hamm ◽

Johnson

Keyword(s):

Crack Growth ◽

Large Crack ◽

Growth Laws

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Nondestructive evaluation

AccessScience ◽

10.1036/1097-8542.455100 ◽

2015 ◽

Keyword(s):

Nondestructive Evaluation

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Nondestructive evaluation of spall damage under repeated impact with ultrasonic method

DYMAT 2009 - 9th International Conferences on the Mechanical and Physical Behaviour of Materials under Dynamic Loading ◽

10.1051/dymat/2009170 ◽

2009 ◽

Author(s):

N. Nishimura ◽

K. Murase ◽

T. Ito

Keyword(s):

Nondestructive Evaluation ◽

Ultrasonic Method ◽

Repeated Impact ◽

Spall Damage

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A discrete dislocation analysis of fatigue crack growth

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2001509 ◽

2001 ◽

Vol 11 (PR5) ◽

pp. Pr5-69-Pr5-75

Author(s):

V. S. Deshpande ◽

H. H.M. Cleveringa ◽

E. Van der Giessen ◽

A. Needleman

Keyword(s):

Fatigue Crack ◽

Fatigue Crack Growth ◽

Crack Growth ◽

Discrete Dislocation

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Effects of contact gap on nondestructive evaluation using magnetic measurement for ferromagnetic steel

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-209411 ◽

2020 ◽

Vol 64 (1-4) ◽

pp. 969-975

Author(s):

Hiroaki Kikuchi ◽

Yuki Sato

Keyword(s):

Magnetic Flux ◽

Nondestructive Evaluation ◽

Effective Permeability ◽

Magnetic Circuit ◽

Magnetic Measurement ◽

Air Gap ◽

Motive Force ◽

Hysteresis Curve ◽

Evaluation Technique ◽

Ferromagnetic Steel

We investigated effects of contact gap on magnetic nondestructive evaluation technique using a magnetic single-yoke probe. Firstly, we evaluated hysteresis curves and impedance related to permeability of the material measured by a single-yoke probe, when an air gap length between the probe and specimens changes. The hysteresis curve gradually inclines to the axis of the magneto-motive force and magneto-motive force at which the magnetic flux is 0 decreases with increasing the gap length. The effective permeability also decreases with increasing the gap thickness. The incremental of gap thickness increases the reluctance inside the magnetic circuit composed of the yoke, specimen and gap, which results in the reduction of flux applying to specimen.

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